Method for annealing flexible metallic material

ABSTRACT

D R A W I N G A METHOD AND APPARATUS FOR ANNEALING FLEXIBLE METALLIC MATERIAL IN WHICH THE MATERIAL IS PASSED BY MEANS OF AN ELECTRIC MOTOR THROUGH AN ANNEALING DEVICE. A LENGTH OF THE MATERIAL IS FORMED INTO A LOOP AND SHORT CIRCUITED TO FORM A SHORTED SINGLE TURN SECONDARY OF AN INDUCTION COIL SO THAT INDEED CURRENT IN THE MATERIAL HEATS AND ANNEALS IT. THE TENSION IN THE MATERIAL IS CONTROLLED BY A DEVICE WHICH DETECTS CHANGES IN TENSION AND WHICH IS COUPLED TO TWO IDENTICAL CONTROL CIRCUITS CONTROLLING THE SPEED OF THE MOTOR.

. Filed Nov. 7, 1969 Oct. 10, 1972 Y K s ETAL 3,597,335

METHOD FOR ANNEALING FLEXIBLE METALLIC MATERIAL 4 Sheets-Sheet 1 iNVENTORS JOHN KYRIAKIS WALTER ROLAND TOLE Oct. 10, 1972 J. KYRIAKIS ET AL METHOD FOR ANNEALING FLEXIBLE METALLIC MATERIAL Filed Nov. 7, 1969 4 Sheets-Sheet z INVENTORS JOHN KYRIAKIS WALTER ROLAND TOLE Oct. 10, 1972 J. js ET AL 3,697,335

METHOD FOR ANNEALING FLEXIBLE METALLIC MATERIAL Filed Nov. 7, 1969 4 Sheets-Sheet 3 INVENTORS JOHN KYRIAKIS WALTER ROLAND TOLE Oct. 10,1972 J. KYRIAKIS ETAL 3,697,335

METHOD FOR ANNEALING FLEXIBLE METALLIC MATERIAL Filed Nov. 7, 1969 4 Sheets-Sheet 4 INVENTORS JOHN KYRIAKIS WALTER ROLAND TOLE EUw 6. Q Q lir United States Patent US. Cl. 148-154 4 Claims ABSTRACT OF THE DISCLOSURE A method and apparatus for annealing flexible metallic material in which the material is passed by means of an electric motor through an annealing device. A length of the material is formed into a. loop and short circuited to form a shorted single turn secondary of an induction coil so that induced current in the material heats and anneals 3,697,335 Patented Oct. 10, 1972 FIG. 4 is an enlarged view of part of FIG. 3, and

FIG. is a schematic view of two identical thyristor control circuits with their associated trigger circuits.

' =In FIGS. 1 and 2 a wire 1, which is to be annealed, forms a secondary single-tum winding of an induction coil or coils 2. The induction coil 2 of an annealer 13 comprises a high permeability silicon iron toroidal core with a primary winding which is fed from a power unit 3 having a variable voltage supply of constant frequency.

The secondary turn formed by the wire 1 is short circuited continuously by two electrically conducting pulleys it. The tension in the material is controlled by a device which detects changes in tension and which is coupled to two identical control circuits controlling the speed of the motor.

This invention relates to a method and apparatus for the continuous annealing of flexible metallic materials such as metallic wires, rods, tubes, strip and the like. Wire to be annealed is fed into an annealing device, is annealed therein, and emerges as a processed product.

An object of the invention is to provide means for automatically controlling the tension of the flexible material to be annealed.

In one aspect, the invention provides a method of annealing flexible metallic material comprising passing said material through an annealing device by means of an electric motor, magnetically coupling a length of said material with an induction coil, short circuiting said length of material so that induced current in said length heats said material, and controlling the tension insaid flexible material by means of an electronic control circuit of said electric motor and by means of a device for detecting changes in tension in said flexible material, said control circuit having two identical symmetrical control circuits, and said device being operationally coupled to said control circuits for operation of one of said control circuits and corresponding inhibition of the other of said control circuits so as to alter the speed of said electric motor and compensate for any change of tension in said flexible material.

In another aspect, the invention provides apparatus for annealing flexible material comprising an annealing device having an induction coil, an electric motor for passing said flexible material through said annealing device, an electronic control circuit for said motor comprising two identical symmetrical control circuits connected to said motor, and a device for detecting changes of tension in said flexible material and operating one of said con trol circuits and inhibiting the other of said control circuits so as to alter the speed of said motor and compensate for any change of tension in said flexible material.

The invention will be further described with reference to an embodiment shown, by way of example only, in the accompanying drawing, wherein:

FIG. 1 is a schematic view of an annealer and control system,

FIG. 2 is an enlarged section through an embodiment of the annealer of FIG. 1, showing an arrangement of pulleys,

FIG. 3 is a vertical section through co-axially-arranged shorting pulleys of FIG. 2, Y

4 and 5 and brushes 6. The current that flows in the wire as a result of short circuiting raises the wire temperature and thus the desired annealing effect is obtained.

A pulley 7 is an insulated free-running pulley and acts as a guide for the wire 1. Pulleys 8 and 9 are insulated free-running pulleys and form part of a tension control system. This system is such that the pulley 8 acts as a wire tension sensor and provides a signal to a power controller 10 containing the thyristor control circuits and driving a servomotor 11 which is coupled to the pulley 5. The pulley 4 is coupled mechanically to a capstan take-up 12 via a motor 11' for pulling the wire 1 through the annealer 13. The pulleys 4 and 5 are partially or totally immersed in a quenching tank 20 containing a coolant, such as water, oil or the like supplied from a reservoir 16, in order that the annealed wire is quenched before it emerges from the annealer 13. An inert atmosphere of steam, nitrogen or other inert gases is desirable in the enclosure of the annealer 13 in order to prevent oxidation of the wire 1. The voltage supply 3 and induction coil or coils 2 are of such electrical specification to permit a high secondary coil voltage so that wires may be processed at high speeds. The power unit is preferably a frequency changer such as a motor alternator, power oscillator or the like, the output frequency of which should preferably be in the range of approximately 500 c./s. or higher. This enables a small dimension induction coil to be employed. The tension control system embodied in the annealer 13 maintains a constant tension in the wire loop, obviates pulley to wire slip, eliminates sparking or arcing and reduces pulley wear.

A tacho generator 14 is coupled to the capstan 12 and provides for a speed proportional control by adjusting the power to the induction coils 2 in proportion to wire speed via an alternator exciter circuit 15.

FIG. 3 shows the coaxial shorted mounting of the pulleys 4 and 5. The pulley 4 is mounted on a spindle 17 driven by the capstan 12, and the pulley 5 is mounted on a spindle 18 driven by the servo motor 11.

The pulley 4 is provided with a peripheral lip 19 (FIG. 4) which overlaps the peripheral edge of the pulley 5, thus preventing the wire from entering the space between the pulleys 4 and 5 and inhibiting correct operation.

In FIG. 5, the operation of one of the thyristor control circuits is as follows:

RC network of R1 (potentiometer 21), R2 and C1, provides turning-on current to the base of transistor Q1. When the voltage across C1 becomes large enough during the positive half cycle, the base current in Q1 turns on this transistor which in turn supplies base current to Q2, turning on Q2, this supplying more base current to Q1 this being regenerative action saturates transistors Q1 and Q2.

Capacitor C1 discharges through these saturated transistors into the gate of the SCRl, when the SCRl fires, the remaining portion of the positive half cycle of A.C. power is supplied to the motor 11.

Speed control is accomplished by the variation of potentiometer 21 which is in itself one element of the dual potentiometer described in the tension sensing device.

The other identical SCR2 unit operates in the same manner, the dual potentiometer arrangement only permits one circuit to be opertive Whilst'the other is'cut oil and vice versa. Both circuits can supply suflicient controlled power for full speed and full output torque of the DC. motor 11, one circuit providing power for clockwise rotation and the other circuit providing power for anti-clockwise rotation in eifect dynamic braking. Additional component elements are included (R3 and C2) to produce critical damping and stable operation under all operative conditions.

Although FIG. 5 represents a half wave SCR circuit, a full wave SCR circuit may be used to achieve the same results.

We claim:

1. A method of annealing by electric induction heating of elongated flexible metallic material comprising: arranging said elongated flexible metallic material under controlled tension to pass on a set of pulleys through an annealing device; magnetically coupling a length of said material lying between a first and last pulley of said set of pulleys with a magnetic core of an induction coil and arranging to short circuit said length of material which is moving on pulleys to form a single turn shorted secondary around said magnetic core so .as to heat said length of material by means of induced short circuit currents flowing therein; controlling the tension of the fiex'ible material passing through the annealing device by means of a control circuit which includes two identical and symmetrically arnange'd circuit branches coupled to a motor which drives said flexible metallic material, the circuit branches selectively operating to alter the speed of said motor to compensate for any tension variations in the flexible material. 7

2. A method as claimed in claim 1 which includes a step of quenching after annealing.

3. A method as claimed in claim 1 which includes a step of annealing the flexible material in an inert atmosphere.

4. A method as claimed in claim 1 which includes a step of adjusting a power infeed to said induction coil in amounts proportional to a travel speed of the flexible material through the annealing device.

References Cited 7 UNITED STATES PATENTS 3,469,829 9/1969 Fujita et a1. 148-131 RICHARD O. DEAN, Primary Examiner US. Cl. X.R.

l48-150, 153, 155, 156; 2l910.4l 

